This invention relates to a light source device using a light emitting diode and a light emitting device using a plurality of such light source devices. The light emitting device is useful as a signal indicting lamp installed in, for example, in workplace to ensure safety of workers, drivers and pedestrians and as an illuminating lamp or sign for advertising.
Because of their longer service life and smaller energy consumption, light emitting diodes are increasingly used as a substitute for incandescent lamps. Light emitting diodes are thus utilized as a light emitting device, such as a signal indicating lamp or an advertising lamp, having a disc-like globe with opposing light permeable surfaces.
A light emitting diode is generally composed of a light emitting source encapsuled in a transparent bullet-like shell and is designed to emit light mainly in an axial direction. Because of this characteristic of light directivity, a light emitting device disclosed in Japanese utility model publication H01-93209 uses a large number of light emitting diodes disposed in a disc-like globe such that a half of them are oriented toward one surface of the globe with a remainder half being oriented toward the other surface.
To reduce the number of the light emitting diodes, Japanese utility model registration No. 2,579,221 proposes the use of a reflector in a light emitting device having a disc-like globe. The globe has opposing light permeable front and rear walls, and a circumferential side wall disposed between therebetween. A plurality of light emitting diodes are arranged such that light emitted therefrom are projected radially outward, namely toward the cicumferential side wall. A reflecting plate is disposed along an inside wall of the circumferential side wall, so that the light from the light emitting diodes is reflected thereon and redirected toward the light permeable front and rear walls.
The above device can reduce the number of the light emitting diodes, but has a problem that the construction of the globe, reflecting plate and associated parts thereof is complicated. Further, with the above device, it is not possible to use light emitting diodes having various different sizes for obtaining a desired illumination image or design.
It is, therefore, an object of the present invention to provide a light emitting device which uses a plurality of light emitting diodes and which is simple in construction and which can give high brightness and uniform illumination.
Another object of the present invention is to provide a light emitting device of the above-mentioned type which permits easy changes of an illumination mode or design.
It is a further object of the present invention to provide a light emitting device of the above-mentioned type which can efficiently use a light flux from each light emitting diode.
It is yet a further object of the present invention to provide a light source device using a light emitting diode.
In accomplishing the foregoing objects, there is provided in accordance with the present invention a light emitting device which comprises a disc-like globe including a light permeable first wall, a second wall disposed opposite the first wall, and a circumferential side wall disposed between the first and second walls, and a plurality of light source devices secured within the globe and arranged along a peripheral portion thereof. Each of the light source devices includes:
a light-permeable cap having opposing top and bottom surfaces, opposing first and second surfaces located between the top and bottom surfaces, opposing third and fourth surfaces located between the top and bottom surfaces and between the first and second surfaces, the bottom surface having a concave portion extending toward the top surface; and
a light emitting diode accommodated and secured in the concave portion so that a part of light emitted from the diode is projected toward the top surface;
the top surface being a flat surface oriented at such an angle that the light projected toward the top surface is reflected thereon and is redirected toward the first surface,
each of the light source devices being disposed so that a light from the first surface of each of the light source devices is projected outwardly from the globe through the light-permeable first wall.
The present invention also provides a light emitting device which comprises a disc-like globe including opposing light permeable first and second walls, and a circumferential side wall disposed between the first and second walls, and a plurality of light source devices secured within the globe and arranged along a peripheral portion thereof. Each of the light source devices includes:
a light-permeable cap having opposing top and bottom surfaces, opposing first and second surfaces located between the top and bottom surfaces, opposing third and fourth surfaces located between the top and bottom surfaces and between the first and second surfaces, the bottom surface having a concave portion extending toward the top surface; and
a light emitting diode accommodated and secured in the concave portion so that a part of light emitted from the diode is projected toward the top surface;
the top surface being V-shaped so that the light projected toward the top surface is reflected thereon and divided into two fractions which are redirected toward the first and second surfaces, respectively,
each of the light source devices being disposed so that the light fractions from the first and second surfaces of each of the light source devices are projected outwardly from the globe through the light-permeable first and second walls, respectively.
The present invention further provides a light source device which comprises:
a light-permeable cap having opposing top and bottom surfaces, opposing first and second surfaces located between the top and bottom surfaces, opposing third and fourth surfaces located between the top and bottom surfaces and between the first and second surfaces, the bottom surface having a concave portion extending toward the top surface; and
a light emitting diode accommodated and secured in the concave portion so that a part of light emitted from the diode is projected toward the top surface;
the top surface being oriented at an angle so that the light projected toward the cut surface is reflected thereon and is redirected toward at least one of the first and second surfaces.